# Local Machine

## Requirements

The prerequisite for this part is that you have a version of [Java 8](https://adoptopenjdk.net/releases.html?variant=openjdk8\&jvmVariant=hotspot) installed.

[Download](https://alluxio.io/download) the binary distribution of Alluxio.

To run in standalone mode, do the following:

* You should have received an email from your Alluxio sales representative which includes your Alluxio Enterprise Edition license. Download the attached license, rename the file to `license.json`, and place it in the root of the extracted binary.
* Create `conf/alluxio-site.properties` by copying `conf/alluxio-site.properties.template`
* Set `alluxio.master.hostname` in `conf/alluxio-site.properties` to `localhost` (i.e., `alluxio.master.hostname=localhost`).
* Set `alluxio.master.mount.table.root.ufs` in `conf/alluxio-site.properties` to a tmp directory in the local filesystem (e.g., `alluxio.master.mount.table.root.ufs=/tmp`).
* Turn on remote login service so that `ssh localhost` can succeed. To avoid the need to repeatedly input the password, you can add the public SSH key for the host into `~/.ssh/authorized_keys`. See [this tutorial](http://www.linuxproblem.org/art_9.html) for more details.

## Mount RAMFS file system

> Run the below command to mount RAMFS file system.

```console
$ ./bin/alluxio-mount.sh SudoMount
```

## Format Alluxio Filesystem

> NOTE: This step is only required when you run Alluxio for the first time. If you run this command for an existing Alluxio cluster, all previously stored data and metadata in Alluxio filesystem will be erased. However, data in under storage will not be changed.

```console
$ ./bin/alluxio format
```

## Start Alluxio Filesystem Locally

Simply run the following command to start Alluxio filesystem.

```console
# If you have not mounted the ramdisk or want to remount it (ie. to change the size)
$ ./bin/alluxio-start.sh local SudoMount
# OR if you have already mounted the ramdisk
$ ./bin/alluxio-start.sh local
```

> NOTE: On Linux, this command may require to input password to get sudo privileges in order to mount the RAMFS. If you do not want to type in the password every time, or you do not have sudo privileges, please read the alternative approaches in [FAQ](#faq).

## Verify Alluxio is running

To verify that Alluxio is running, visit [**http://localhost:19999**](http://localhost:19999), or see the log in the `logs` folder.

To run a more comprehensive sanity check:

```console
$ ./bin/alluxio runTests
```

You can stop Alluxio any time by running:

```console
$ ./bin/alluxio-stop.sh local
```

## FAQ

### Why is sudo privilege needed to start Alluxio on Linux?

By default, the Alluxio filesystem uses [RAMFS](https://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt) as its in-memory data storage. On MacOS, it is fine for Alluxio to mount a RAMFS without being a super user. However, on Linux, it requires sudo privileges to perform `mount` (and the associated `umount`, `mkdir` and `chmod` operations).

### Can I still try Alluxio on Linux without sudo privileges?

If you have no sudo privileges on Linux, for Alluxio Filesystem to work, it requires a RAMFS (e.g., `/path/to/ramdisk`) already mounted by the system admin and accessible for read/write-operations by the user. In this case you can specify the path in `conf/alluxio-site.properties`:

```properties
alluxio.worker.tieredstore.level0.alias=MEM
alluxio.worker.tieredstore.level0.dirs.path=/path/to/ramdisk
```

and then start Alluxio with `NoMount` option to use the above directory as its data storage:

```console
$ ./bin/alluxio-start.sh local NoMount
```

Alternatively, you can also specify Linux [tmpFS](https://en.wikipedia.org/wiki/Tmpfs) as the data storage. Tmpfs is a temporary file storage backed by memory (e.g., typically `/dev/shm` on Linux), but may use SWAP space and therefore provides less performance guarantees compared to ramfs. Similar to using a pre-mounted RAMFS, you can specify the tempfs path in `conf/alluxio-site.properties`:

```properties
alluxio.worker.tieredstore.level0.alias=MEM
alluxio.worker.tieredstore.level0.dirs.path=/dev/shm
```

followed by:

```console
$ ./bin/alluxio-start.sh local NoMount
```

### How can I avoid typing the password to run `sudo`?

Options:

* Start Alluxio as a super user.
* Add the user who starts Alluxio to the [sudoers](https://help.ubuntu.com/community/Sudoers) file.
* Give limited sudo privileges to the running user (e.g., `alluxio`) by adding the following line to `/etc/sudoers` on Linux:

```
alluxio ALL=(ALL) NOPASSWD: /bin/mount * /mnt/ramdisk, /bin/umount */mnt/ramdisk, /bin/mkdir * /mnt/ramdisk, /bin/chmod * /mnt/ramdisk
```

This allows Linux user "alluxio" to mount, umount, mkdir and chmod (assume they are in `/bin/`) a specific path `/mnt/ramdisk` with sudo privileges without typing the password, but nothing else. See more detailed explanation about [Sudoer User Specifications](https://help.ubuntu.com/community/Sudoers#User_Specifications).